Design: In this natural history study, participants will be followed for five years. Because three years may be required to enroll 65 participants, this study will last up to eight years. Participants will be recruited through other pre-existing NIH protocols, such as the NEI Evaluation and Treatment Trial (08-EI-0169), the NEI Screening Protocol (08-EI-0102), and the National Ophthalmic Disease Genotyping and Phenotyping Network, Phase II protocol (eyeGENE II, 10-EI-N164), or through referral from an outside clinician after a review of pertinent medical records and genetic testing. All participants will undergo a standardized medical/ophthalmic history and a complete baseline eye examination, including non-invasive electrophysiology (e.g., electroretinography), psychophysiology (e.g., microperimetry, static perimetry), and diagnostic imaging examinations (e.g., optical coherence tomography).